• Hey, Ho: 13th century

• Hi: 15th century

• Hollo, Hillo, Holla, Halloo: 16th century
  • Shouts used in hunting

• Hal: Be healthy

• Hail: 13th century

• Hallo, Hello, Hillo, Hollo, Hullo
  Stress was on the second syllable, difficult to hear the quality of the first vowel.

• Google Ngram Viewer
  

Early 1800s: informal, street slang

• 1876: Invented by Alexander Graham Bell (Not Edison)

• Need a way of starting a conversation

• Prefered Hello:
  Shouted 'Hello' ('Halloo') into the mouthpiece when testing a phonograph (留聲機)

• A letter (1877) used Hello:
  "I don't think we shall need a call bell as 'Hello!' can be heard 10 to 20 feet away. What do you think?"

I mean, hello! How crazy was that?
Implying that someone has missed the point in some way.

Disinterested: impartial, bored('incorrect', Oxford)

Uninterested: bored, unconcerned